Yes, you can use vmkfstools to copy the thin provisioned virtual disk if you don't have vCenter Server in place to migrate or Storage vMotion the VM. In order to do this ensure that the VM has no active snapshots (i.e. no 00000x.vmdk files in the VM's folder)!!!
- power off the VM
- right click the VM in the inventory and select "Remove from Inventory"
- use the datastore browser to create the target folder on the target datstore
- copy all files except for the .vmdk file(s)
- then from the ESXi host's command line run:
vmkfstools -i /vmfs/volumes/source-datastore/source-folder/virtual-disk.vmdk -d thin /vmfs/volumes/target-datastore/target-folder/virtual-disk.vmdk - right click the VM's .vmx file and select "Add to Inventory"
- after powering on the VM for the first time, answer the question on whether you moved or copied the VM with "I moved it"
- if the VM works as expected, delete the old virtual disk and folder
André